Chlorine dioxide

Chlorine DioxideThe following fact sheet is part of a series relating to chemicals that may be used in authorized personnel according to the specific requirements of the applicable crisis exemption andapproved decontamination plans. These chemicals are not intended for use by the general public.What is Chlorine Dioxide?Chlorine dioxide (ClO2) is an antimicrobial pesticide recognized for its disinfectant properties since theearly 1900's. Antimicrobial pesticides are substances used to control harmful microorganismsincluding bacteria, viruses or fungi on inanimate objects and surfaces. In 1967, EPA first registeredthe liquid form of chlorine dioxide for use as a disinfectant and sanitizer. In 1988, EPA registeredchlorine dioxide gas as a sterilant.Chlorine dioxide kills microorganisms by disrupting transport of nutrients across the cell wall. Chlorinedioxide can be generated in a gas or liquid form and smells like chlorine bleach. Chlorine dioxideshould not be confused with chlorine gas. They are two distinct chemicals that react differently andproduce by-products that also have little in common.Antimicrobial PesticidesAntimicrobial pesticides are substances used to control harmful microorganisms including bacteria,viruses and fungi on inanimate objects and surfaces primarily in indoor environments. Types ofantimicrobial products have traditionally included sanitizers, disinfectants, and sterilants.
A "sanitizer" is a substance that significantly reduces the bacterial population in theinanimate environment, but does not destroy or eliminate all bacteria or othermicroorganisms.A "disinfectant" is a substance that destroys or eliminates a specific species of infectious orother public health microorganism, but not necessarily bacterial spores, in the inanimateenvironment.A "sterilant" is a substance that destroys or eliminates all forms of microbial life in theinanimate environment, including all forms of vegetative bacteria, bacterial spores, fungi,fungal spores, and viruses.EPA's Registration of PesticidesBefore a pesticide can be marketed and used in the United States, EPA must evaluate the pesticideto ensure that it meets federal safety standards. EPA grants a registration (or a license) for a publichealth pesticide product only after the Agency has reviewed efficacy and safety data to ensure that,when used according to the specific instructions on the label, the product is effective and does notcause any unreasonable adverse effects on human health or the environment. Such evaluation isparticularly important for antimicrobial pesticides (sanitizers, disinfectants, and sterilants) which areused to reduce or eliminate microbial contamination.The pesticide label provides specific safety precautions and use directions for handling or using theproduct. EPA has concluded that chlorine dioxide products registered to date have met federalstandards for environmental and human health safety.Registered Uses for Chlorine DioxideRegistered Liquid and Gaseous Products
EPA first registered chlorine dioxide gas as an antimicrobial pesticide in the 1980s. Chlorinedioxide gas is registered for sterilizing manufacturing and laboratory equipment,environmental surfaces, tools, and clean rooms. It is also used in pharmaceutical researchand production. Liquid chlorine dioxide formulations were first registered in the 1960's asdisinfectants and are used on a variety of sites including pets; farm animals; bottling plants;food processing, handling and storage plants; and many others.Other Registered Uses
Chlorine dioxide gas and liquid formulations also have many other industrial uses including:
Applying Chlorine DioxidePesticide products containing either sodium chlorite or stabilized chlorine dioxide are usuallymixed with another "reactive" chemical - usually an acid - to produce chlorine dioxide in a liquid orgaseous state. The resulting mixture is applied within a specific sterilization or disinfection system.The liquid chlorine dioxide is then applied to hard surfaces with a sponge or mop or as a coarsespray. Chlorine dioxide gas is also generated on site and is released into a sealed treatment areawhere it remains for several hours before being removed. After the treatment is completed, thechlorine dioxide gas is neutralized with sodium bisulfite. The treatment may leave a fine residue, but itis not toxic.FIFRA Section 18 Emergency Exemptions and AnthraxUnder Section 18 of FIFRA, EPA "may exempt any federal or state agency from any provision of thisAct if the Administrator determines that emergency conditions exist which require such exemption."Normally, a federal or state agency submits an application for a FIFRA exemption to EPA for reviewand approval. If EPA approves the request, it issues either a specific or a public health exemption, asappropriate. However, if the emergency is of such urgency that the federal or state agency does nothave enough time to submit an application for exemption and wait for EPA's approval, then the federalor state agency may issue a crisis exemption, which is effective for 15 days. In order for the crisisexemption to be extended beyond 15 days, the federal or state agency must submit an application forexemption to EPA.To handle all anthrax contamination cases as quickly as possible, the Agency has decided to issue allcrisis exemptions itself. To obtain a crisis exemption from EPA for the unregistered use of a pesticideagainst anthrax, a state or federal agency must submit a written request describing the antimicrobialproduct(s) to be used; how, when and where they will be used; the data demonstrating efficacy of theproduct for the intended purpose; and how human health and safety will be protected. Prior to issuingthe exemption, EPA will perform a multi-disciplinary risk assessment of the requested use, relying ondata that they have supplied for the pesticide.If, during this review, EPA notes any adverse human health or environmental concerns, EPA maydeny the exemption request. If, however, EPA believes that the proposed use of an antimicrobialproduct will be effective and will protect human health and the environment, EPA will issue a crisisexemption. Moreover, if EPA determines that use of the product is needed beyond the15-day use period, EPA will complete an application for a public health exemption on behalf of therequesting entity, which allows the crisis exemption to continue in effect until it is either withdrawn orEPA issues a public health exemption.Determination of Safety and Efficacy for Crisis Exemptions for Chlorine DioxideEPA has reviewed data related to safety and effectiveness before allowing an emergency exemptionfor liquid and gaseous chlorine dioxide to be used specifically for anthrax decontamination. Availablepublished data suggest that liquid and gaseous chlorine dioxide will reduce bacterial sporepopulations under specific conditions including concentration, pH, and contact time.Based on this review, EPA issued crisis exemptions for the limited sale, distribution, and use of liquidand gaseous chlorine dioxide against anthrax. EPA has determined that the public health threatposed by the anthrax incidents constitutes a public health emergency of such immediacy that normalprocessing and review of a conventional public health exemption under FIFRA are neither prudent norpractical. Under the crisis exemption for liquid chlorine dioxide, registered products (containingsodium chlorite) may be sold or distributed only to employees of federal, state or local governmentagencies, or of the U.S. Postal Service, for anthrax cleanup. Crisis exemptions for gaseous chlorinedioxide (from certain sodium chlorite products) have been issued for use at the Hart Senate OfficeBuilding (November 30, 2001), to decontaminate the exterior of mail packages that have beenreceived by U.S. government offices (February 26, 2002), and to test fumigation of lockers in a trailerat the U.S. Postal Service Brentwood Processing and Distribution Center, Washington, D.C. (June 21,2002).Since issuing the initial crisis exemption on November 9, 2001, EPA tested the effectiveness of liquidchlorine dioxide and found that it was effective on hard surfaces (500 milligrams per liter, at 30minutes contact time), but not effective on porous surfaces (e.g.,carpeting, chairs, couches, and otherfabric surfaces) under the conditions of use specified in the Section 18 Crisis Exemption of November9, 2001. On March 28, 2002, EPA amended the crisis exemption for liquid chlorine dioxide to limit itsuse to hard surfaces only. This amendment does not affect the results of the cleanups performed withliquid chlorine dioxide to date. At the cleanup sites where liquid chlorine dioxide was used, all poroussurfaces were pre-treated and removed for final disposal at a facility capable of destroying anyremaining spores. Liquid chlorine dioxide, along with other methods and technologies, continues to beeffective against anthrax spores on hard surfaces. Current fact sheets are available on EPA's AnthraxWeb page at: .Emergency Use of Liquid Chlorine Dioxide in Anthrax DecontaminationApplication of the pesticide products under the crisis exemption is limited to specific buildings ortreatment sites identified by EPA or other federal, state, or local governmental authorities, or theUnited States Postal Service. Applications must be conducted according to use instructions fromfederal, state, or local emergency response personnel following a plan that includes the followingsteps:
Pre-sampling to determine the extent of spore contamination at specific locations.
Spot remediation of highly contaminated surfaces through HEPA filter vacuuming.
Gross surface decontamination with liquid chlorine dioxide.
Post-treatment sampling to determine that the anthrax decontamination has been
Re-treatment with liquid chlorine dioxide if viable spores are detected.
These steps apply to facilities where the treated surfaces will be reused or the facility will be re-occupied. These steps do not necessarily apply to wastes or debris intended for disposal in anappropriate facility.Applying Liquid Chlorine DioxideOn March 28, 2002, the Crisis Exemption for liquid chlorine dioxide was amended to specify its use todecontaminate hard surfaces only. Applications must be conducted according to use instructionsfrom federal, state, or local emergency response personnel following a plan that includes the followingsteps:
Pre-sampling to determine the extent of spore contamination at specific locations.
Spot remediation of highly contaminated surfaces through HEPA filter vacuuming.
Gross surface decontamination using a liquid solution of chlorine dioxide under the
a rate of 500 mg/L liquid chlorine dioxide will be applied;
applications will be made at room temperature (68 degrees F, 20 degrees C);
treatments will have a contact time of at least 30 minutes.
Post-treatment, environmental sampling to determine whether viable anthrax spores
Re-treating with liquid chlorine dioxide if viable spores are detected.
Post-treatment testing to determine that the anthrax decontamination has been effective.
Any remaining liquid chlorine dioxide must be removed from the treated areas of the building beforepeople are allowed to re-enter. After treatment, experts must determine - through post-treatmentsampling - that the treatment was effective before anyone is allowed back into the building.Applying Gaseous Chlorine DioxideBased on review of available data, EPA believes that gaseous chlorine dioxide can be used in afacility decontamination procedure that includes sampling, cleaning, treating, and re-sampling,followed by additional treatment if necessary. The crisis exemptions for gaseous chlorine dioxideissued for the Hart Senate Office building (November 28, 2001) and for the exterior of mail packages(February 26, 2002) involved products containing sodium chlorite as the active ingredient to generategaseous chlorine dioxide on site, followed by post-treatment environmental sampling to confirm thatthe treated areas were free from anthrax spores ( i.e., showing no growth when samples are culturedin the laboratory). The conditions of application are described below. These conditions did notnecessarily apply to personal protective equipment and other debris that were further treated offsite.Conditions of application:
A minimum concentration 500-550 ppm chlorine dioxide gas was initially applied for aminimum of 12 hours, for a minimum total of 6,000 ppm-hours. Later, the concentrationwas increased to 750 ppm for a total of 9,000 ppm-hours.
Applications were made at a minimum temperature of 70 degrees F; and
Relative humidity was maintained at a minimum of 65%. On June 17, 2002, EPA issueda crisis exemption for the U.S. Postal Service to test gaseous chlorine dioxide fumigationof lockers in a truck trailer located at the Brentwood Processing and Distribution Centerin Washington, D.C. The lockers in the test were not contaminated with Bacillus anthracis.Rather, they were set up to simulate the 3,000+ lockers inside the building that would
to be fumigated either together with the building or separately. The purpose of the test
to help determine the ClO2 concentration and contact time would be necessary to obtain asuccessful decontamination of employees' lockers.More Information on Antimicrobial Pesticides
If you have general questions about the federal pesticide program browse the Web site, or contactEPA's pesticides office:
Tel: 703-305-5017Fax: 703-305-5558E-mail:
AnthraxAnthrax is an acute infectious disease caused by the
spore-forming bacterium Bacillus anthracis. Anthrax most
commonly occurs in farm animals, but it can also infect
humans. Symptoms of disease vary, but usually occur
within 7 days after exposure. The serious forms of human
anthrax are inhalation (a respiratory infection), cutaneous (a skin infection), and intestinal anthrax.
Anthrax contamination was detected in U. S. Senate
office buildings and at several other locations across the
United States. The EPA has been working closely with
the Capitol Hill Police, the U.S. Postal Service, the
Centers for Disease Control, the FBI, and other agencies
to ensure that existing anthrax contamination is quickly
identified and thoroughly cleaned up, and also to prevent
While anthrax cleanup is a new challenge, EPA and its
partners have assembled an effective toolbox for tackling
it. In a very short time, we've significantly advanced the
science and technology of detecting and cleaning up
EPA's Role in Responding to Anthrax ContaminationEPA provides technical expertise and oversight in detecting anthrax contamination and ensuring thatcleanup fully protects public health and the environment.Local police, health department officials or hazardous materials teams are usually the first ones onscene in response to incidents that could involve anthrax. They do the initial sampling, and if anthraxis found, more comprehensive sampling is needed to fully assess the severity and extent ofcontamination.Private building owners are responsible for hiring qualified contractors to conduct this sampling andperform whatever decontamination is necessary. Due to the extreme hazards potentiallyassociated with exposure to anthrax, it is absolutely essential to work closely with EPA andother federal agencies with expertise in sampling, decontamination and protection of workers.EPA is notified through the toensure that work proceeds appropriately. Under the to take over this work if the situation exceeds the capabilities of the owner or state and localresponders.Once the extent of contamination is assessed, EPA provides technical expertise in developing a site-specific cleanup plan. Decontamination of anthrax is a rapidly evolving field, with new technologiescontinually being advanced and tested. It is EPA's responsibility to ensure that antimicrobialpesticides used in anthrax decontamination plans meet all Federal requirements for standards ofsafety and effectiveness. In developing a strategy for decontamination, EPA consults with a variety ofscientific experts, such as:
• EPA's Environmental Response Team Scientific Support Coordinators• EPA research laboratories• the National Institute of Occupational Safety and Health• the Centers for Disease Control and Prevention• the US Army Medical Research Institute for Infectious Diseases• the Defense Advanced Research Projects Agency
State and local environmental and health officials are also consulted, and we may requestrecommendations from national experts in universities and private industry.
The cleanup plan reflects the size and type of the potentially contaminated areas (e.g., a large openmailroom or a small office cubicle), how the contamination was delivered (e.g., highly concentratedspores contained in an envelope or tracked down the hallway from a contaminated area), howcontamination could be dispersed (e.g., through an air handling system or by ordinary movementwithin an office) and other characteristics related to daily activities in the area. Since each site isdifferent, each cleanup plan will be tailored to the unique situation at that site.Once cleanup is completed, a new round of sampling is done to make sure that the anthrax sporeshave been removed or killed, and that it is safe to reoccupy the area. In some cases, it may benecessary to use more than one type of treatment or to treat more than one time.The National Response SystemEPA's response to recent anthrax incidents is part of a larger National Response System that haseffectively dealt with a wide range of environmental emergencies for almost 30 years. It is a multi-layered system of individuals and teams from local, state, and federal agencies, industry, and otherorganizations that share expertise and resources to ensure that oil spill control and cleanup activitiesare timely and efficient, and that they minimize threats to human health and the environment.New Methods and TechnologiesAnthrax decontamination is a rapidly evolving field, with new methods and technologies continuallybeing developed and tested. Several different antimicrobial pesticides and devices are being currentlyused by qualified experts under carefully controlled conditions in anthrax cleanups being done acrossthe country.
EPA's Technology Innovation Office is leading an effort to collect and disseminate information abouttechnologies that detect and kill anthrax and other biological agents. is a clearinghouse for information about these technologies and their vendors, and links toother resources pertaining to the detection and decontamination of biological agents. We are alsooperating a vendor helpline at (703) 390-0701 and an email address at tofield inquiries from vendors of detection, decontamination, and measurement technologies.Under the Federal Insecticide, Fungicide, and Rodenticide Act, all products that claim to be asanitizer, disinfectant, sterilant, or sporicde need a registration number or approval for emergency usefrom the Antimicrobials Division of EPA's Office of Pesticide Programs. Vendors of decontaminationtechnologies who wish to get their technology registered or approved for emergency use shouldcontact Jeff Kempter in EPA's Office of Pesticide Programs, Antimicrobials Division, at (703)305-5448, or . For a complete list of crisis exemptions issued by EPA forpesticide products used for decontamination of anthrax see ().Other Counter-terrorism ActivitiesLike many other federal agencies, EPA is working closely with the todevelop a national strategy to strengthen protections against terrorist threats or attacks in the UnitedStates. But EPA has also been actively involved in federal counter-terrorism planning and responseefforts for the past several years. See EPA's formore information. Our primary responsibilities have been to help state and local response personnelplan for emergencies, to provide counter-terrorism response training, and to provide technicalexpertise and other resources in the event of a terrorist incident.General InformationWhat You Should DoAnthrax Fact SheetsFrequently Asked QuestionsResponse UpdatesWashington, DCAs part of a Unified Command effort, EPA responded to anthrax contamination discovered inCongressional buildings in the Capitol Complex. EPA emergency responders have taken thousandsof samples in more than 30 buildings to determine whether anthrax was actually present and todesign and carry out site-specific cleanup strategies where contamination was found. SenatorDaschle's office suite was fumigated with chlorine dioxide gas on December 1, (see ) and on Dec. 30, further fumigation was done in the air handlingsystem that serves that area. Several other suites and common areas in the Hart Building and in otherbuildings in the Capitol Complex were cleaned using chlorine dioxide liquid, foams and high efficiencyparticle air (HEPA) filter vacuuming. Post cleanup sampling showed no remaining viable anthrax, andon Jan. 22, the Hart, Ford and Longworth Buildings were cleared for reoccupancy.Related activities include:
• sampling to confirm and determine the extent of contamination• evaluating sampling results• isolating areas to prevent spread of contamination• removing critical objects for special decontamination procedures• working with the US Postal Service and other agencies to evaluate the effectiveness of
potential disinfectants and cleanup technologies
• cleaning up localized areas of decontamination
In addition to the work in the Capitol Complex, EPA is supporting numerous other agencies in themetropolitan Washington area in identifying and eliminating anthrax contamination. EPA is providingextensive assistance to the US Postal Service in designing and carrying out comprehensive cleanupplans for contamination at their Brentwood facility.FloridaEPA conducted extensive sampling at the American Media, Inc. building in Boca Raton. We are nowproviding technical assistance to the owner in developing and carrying out a strategy fordecontaminating the building.EPA also provided technical assistance to the US Postal Service in sampling and decontaminatingfive postal facilities in Boca Raton, Lake Worth, and West Palm Beach. Decontamination has beencompleted at all of these facilities.New YorkEPA has provided technical assistance for sampling and decontamination at the Morgan US postalfacility, NBC News Headquarters, the offices of the New York Post, and the office of Mayor Giuliani.Other LocationsEPA has also provided technical assistance at:
• 7 US postal facilities in New Jersey• 1 private facility in Indiana• 1 private facility in Missouri• 1 US postal facility in North Carolina• 1 US postal facility in Connecticut
Technical InformationFor Responders:Note: Due to the extreme hazards potentially associated with exposure to anthrax, it is absolutelyessential for responders to work closely with EPA and other federal agencies with expertise insampling, decontamination, and protection of workers.Personal Protective Equipment
• Use of Ciprofloxacin or Doxycycline for Postexposure Prophylaxis for Prevention of
Options for Decontamination(Note: These options are authorized for use only under specific conditions tailored to thecharacteristics of each site.)
For Employers/Building Managers:
• • • • Occupational Exposure to Anthrax• •
For Technology Vendors:EPA's Technology Innovation Office is leading an effort to collect and disseminate information abouttechnologies that detect and kill anthrax and other biological agents. is a clearinghouse for information about these technologies and their vendors, and links toother resources pertaining to the detection and decontamination of biological agents. We are alsooperating a vendor helpline at (703) 390-0701 and an email address at tofield inquiries from vendors of detection, decontamination, and measurement technologies.
Under the Federal Insecticide, Fungicide, and Rodenticide Act, all products that claim to be asanitizer, disinfectant, sterilant, or sporicde need a registration number or approval for emergency usefrom the Antimicrobials Division of EPA's Office of Pesticide Programs. Vendors of decontaminationtechnologies who wish to get their technology registered or approved for emergency use shouldcontact Jeff Kempter in EPA's Office of Pesticide Programs, Antimicrobials Division, at (703)305-5448, or . For a complete list of crisis exemptions issued by EPA forpesticide products used for decontamination of anthrax see (